[tor-bugs] #24826 [Core Tor/Tor]: LZMA- and Zstandard compressed consensus diffs stall Tor Browser launch for at least 20s or break it entirely

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#24826: LZMA- and Zstandard compressed consensus diffs stall Tor Browser launch for
at least 20s or break it entirely
--------------------------+------------------------------------
 Reporter:  gk            |          Owner:  (none)
     Type:  defect        |         Status:  new
 Priority:  Medium        |      Milestone:  Tor: 0.3.3.x-final
Component:  Core Tor/Tor  |        Version:
 Severity:  Normal        |     Resolution:
 Keywords:                |  Actual Points:
Parent ID:  #22341        |         Points:
 Reviewer:                |        Sponsor:
--------------------------+------------------------------------

Comment (by gk):

 Okay, here we are:
 {{{
 Jan 10 20:20:31.000 [debug] HTTP body from server 'XX.XX.XX.XX:9001' was
 labeled as LZMA compressed, and it seems to be LZMA compressed.
 Jan 10 20:20:31.000 [debug] dir_client_decompress_response_body():
 Successfully decompressed body using LZMA compressed
 Jan 10 20:20:31.000 [debug] consensus_diff_apply(): About to apply
 consensus diff.
 Jan 10 20:20:31.000 [debug] consensus_diff_apply(): Computed digest-as-
 signed for applying consensus diff.
 Jan 10 20:20:48.000 [debug] consdiff_apply_diff(): Extracted digests for
 consensus diff.
 Jan 10 20:20:48.000 [debug] consdiff_apply_diff(): Digests match; applying
 diff.
 Jan 10 20:20:48.000 [debug] consdiff_apply_diff(): Diff applied.
 Jan 10 20:20:48.000 [debug] consdiff_apply_diff(): Computing digest of
 resulting consensus.
 Jan 10 20:20:48.000 [debug] consdiff_apply_diff(): Digests are equal; diff
 application succeeded.
 Jan 10 20:20:48.000 [info] handle_response_fetch_consensus(): Applied
 consensus diff (size 235301) from server 'XX.XX.XX.XX:9001', resulting in
 a new consensus document (size 1897672).
 }}}
 I compile tor with `--enable-fragile-hardening` but it seems to me that
 does not explain the 17 seconds for extracting digests for consensus diff.
 But I might be wrong.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/24826#comment:16>
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